Data storage device and operating method thereof

Abstract

A data storage device includes a nonvolatile memory device including a plurality of memory cells; and a controller suitable for determining whether the memory cells are erased or not, wherein, when it is determined, based on first data read as a read voltage set including a first read voltage is applied to the memory cells, that the memory cells are not erased, the controller determines whether the memory cells are erased or not based on second data read as the read voltage set in which the first read voltage is replaced with a second read voltage is applied to the memory cells, and wherein the first and second read voltages are read voltages of lowest levels among read voltages included in the read voltage set.

What is claimed is: 
     
       1. A data storage device comprising:
 a nonvolatile memory device including a plurality of memory cells; and 
 a controller suitable for, when it is determined that the memory cells are not erased based on first data, determining whether the memory cells are erased or not based on second data, 
 wherein the nonvolatile memory device reads the first data from the memory cells by applying a read voltage set, in which a first read voltage is included, to the memory cells, adjusts the read voltage set by replacing the first read voltage with a second read voltage, and reads the second data from the memory cells by applying an adjusted read voltage set to the memory cells, and 
 wherein the first read voltage has a lowest voltage level in the read voltage set and the second read voltage has a lowest voltage level in the adjusted read voltage set. 
 
     
     
       2. The data storage device according to  claim 1 , wherein the second read voltage is a voltage of a level higher than the first read voltage by a predetermined voltage. 
     
     
       3. The data storage device according to  claim 1 , wherein the second read voltage is a voltage of a level the same as the first read voltage. 
     
     
       4. The data storage device according to  claim 1 , wherein the memory cells are coupled to a common word line. 
     
     
       5. The data storage device according to  claim 1 , wherein the controller determines that the memory cells are not erased, when a number of bits having a predetermined value among the first data exceeds a first reference number. 
     
     
       6. The data storage device according to  claim 5 ,
 wherein the controller determines that the memory cells are not erased, when a number of bits having a predetermined value among the second data exceeds a second reference number, and 
 wherein the first reference number and the second reference number are different. 
 
     
     
       7. The data storage device according to  claim 1 , wherein the controller performs an error correction operation for the first data, when it is determined based on the first data that the memory cells are not erased. 
     
     
       8. The data storage device according to  claim 7 , wherein the controller controls, when the error correction operation for the first data fails, the nonvolatile memory device to read the second data and performs an error correction operation for the second data, when it is determined based on the second data that the memory cells are not erased. 
     
     
       9. A method for operating a data storage device, comprising:
 obtaining first data by applying a read voltage set, in which a first read voltage is included, to memory cells; 
 determining whether the memory cells are erased or not based on the first data; 
 adjusting the read voltage set by replacing the first read voltage with a second read voltage when it is determined that the memory cells are not erased; 
 obtaining second data by applying an adjusted read voltage set to the memory cells after the adjusting of the read voltage set; and 
 determining whether the memory cells are erased or not based on the second data after the obtaining of the second data, 
 wherein the first read voltage has a lowest voltage level in the read voltage set and the second read voltage has a lowest voltage level in the adjusted read voltage set. 
 
     
     
       10. The method according to  claim 9 , wherein the second read voltage is a voltage of a level higher than the first read voltage by a predetermined voltage. 
     
     
       11. The method according to  claim 9 , wherein the second read voltage is a voltage of a level the same as the first read voltage. 
     
     
       12. The method according to  claim 9 , wherein the determining of whether the memory cells are erased or not, based on the first data, determines that the memory cells are not erased, when a number of bits having a predetermined value among the first data exceeds a first reference number. 
     
     
       13. The method according to  claim 12 ,
 wherein the determining of whether the memory cells are erased or not, based on the second data, determines that the memory cells are not erased, when a number of bits having a predetermined value among the second data exceeds a second reference number, and 
 wherein the first reference number and the second reference number are different. 
 
     
     
       14. The method according to  claim 9 , wherein the memory cells are coupled to a common word line. 
     
     
       15. A method for operating a data storage device, comprising:
 determining whether memory cells are erased or not based on first data obtained by applying a read voltage set, in which a first read voltage is included, to the memory cells; 
 performing an error correction operation for the first data, when it is determined as a result of the determining that the memory cells are not erased; 
 adjusting the read voltage set by replacing the first read voltage with a second read voltage when the error correction operation fails; 
 obtaining second data by applying an adjusted read voltage set to the memory cells after the adjusting of the read voltage set; and 
 determining whether the memory cells are erased or not based on the second data after the obtaining of the second data, 
 wherein the first read voltage has a lowest voltage level in the read voltage set and the second read voltage has a lowest voltage level in the adjusted read voltage set. 
 
     
     
       16. The method according to  claim 15 , further comprising:
 performing an error correction operation for the second data, when it is determined, based on the second data, that the memory cells are not erased. 
 
     
     
       17. The method according to  claim 15 , wherein the determining of whether the memory cells are erased or not, based on the first data, determines that the memory cells are not erased, when a number of bits having a predetermined value among the first data exceeds a first reference number. 
     
     
       18. The method according to  claim 17 ,
 wherein the determining of whether the memory cells are erased or not, based on the second data, determines that the memory cells are not erased, when a number of bits having a predetermined value among the second data exceeds a second reference number, and 
 wherein the first reference number and the second reference number are different. 
 
     
     
       19. The method according to  claim 16 , further comprising:
 determining that the memory cells are not erased, when the error correction operation for the second data fails. 
 
     
     
       20. The method according to  claim 15 , wherein the second read voltage is a voltage of a level higher than the first read voltage by a predetermined voltage.